Russian accused of hacking LinkedIn extradited to US

The Interpol arrest warrant had been issued by the FBI, but Russia rapidly filed its own extradition request after the US unsealed its indictment against Nikulin.

The Czech Ministry of Justice agreed to extradite him to the US amid questions over why Russian authorities had not sought to pursue justice against Nikulin when he was resident in the country.

In the US, he is charged with stealing more than 100 million users' details after breaching the computer networks of LinkedIn, Dropbox and Formspring.

Russian authorities claim he stole less than £1,500 in incidents dating back to 2009.

Nikulin pleaded not guilty to the charges when he appeared in court in San Francisco on Friday.

His legal counsel and the Russian state have argued that his arrest and the charges against him were politically motivated, and that the US is targeting Russian nationals whenever they travelled outside of the country.

US Attorney General Jeff Sessions said: "This is deeply troubling behaviour once again emanating from Russia.

"We will not tolerate criminal cyberattacks and will make it a priority to investigate and prosecute these crimes, regardless of the country where they originate."

Image:Nikulin was extradited from Pankrac prison

There is speculation that a lack of initial charges against Nikulin in Russia suggests he may have been recruited by the Russian security services when he came to their attention.

Western authorities have claimed that Russian cyber criminals are often tolerated by the country's domestic security services as long as their victims are located abroad.

Speaking to Sky News, Dr Mark Galeotti, an expert on Russian security affairs, said it was "very clear" that the state security apparatus in the country was leveraging existing cybercriminal networks for its own purposes.

Dropbox has confirmed that a security breach in 2012 led to the compromise of details of more than 68 million accounts.

Another security breach at LinkedIn in 2012 lost 117 million account details and passwords.

Formspring reset 28 million passwords in the same year after it noticed a security breach.

In the indictment, Nikulin is accused of responsibility for these attacks, and of offering to sell the Formspring user database for €5,500 (£4,800).